Process of preparing dithiocarbamic compounds



Patented Aug. 21, 1923.

UNl'TED STATES PATENT orrica- S'IUABT B. HOLONY, OF WELLESLEY HILLS,MASSACHUSETTS, AND ZASUJUBO NIKAIDO, 01 DAY CITY, MICHIGAN, ASSIGNORS TOMICHIGAN CHEMICAL GOM- PANY, A CORPORATION OF MICHIGAN.

PROCESS OF PREPARING DITHIOCARBAMIC COMPOUNDS.

Ho Drawing.

To all whom it may camera:

Be it known thatwe, STUART B. Mono and YASUJUlRO NIKAIDO, citizens ofthe United States and Japan, respectively, residing at Wellesley Hills,in the county of Norfolk and State of Massachusetts, and Bay City, inthe county of Bay and State of Michigan, respectively, have invented newand useful Improvements in Processes of Preparing DithiocarbamicCompounds, of which the following is a specification.

Our invention relates to the manufacture of dit-hiocarbamic compounds.The object of our invention is theprovision of a proc: ess for themanufacture of dithiocarbamic compounds suitable for use asvulcanization accelerators, in which beet sugar residue is utilized asone of the reacting materials.

A small quantity of beet sugar residue, preferably of 35 B., is placedin a cast iron retort and heated at a temperature ranging from 900 to1300 F., whereupon vapors of an alkaline nature are produced. As soon asthe evolution of the vapors slackens, additional beet sugar residue ofthe same gravity is introduced into the retort in a small continuousstream, the retort being constantly maintained at the above-mentionedtemperature, whereby destructive distillation of the beet sugar residueis effected. The size of the stream of beet sugar residue is controlledby the velocity of the gas reaction. The process of distillation iscontinued until the desired quantity of beet sugar residue is introducedinto the retort and heating is continued until no more gas is produced.

It is quite important that the beet sugar residue be introduced into theretort in controlled continuous streams' in order to avoid thedifliculties hereinafter referred to. If a large quantity of the residueis placed in the retort and destructively heated, owing to the presenceof a considerable quantity of organic matter, the residue swells,forming a viscous mass which fills the retort and passes along with thevapor into the vapor pipe thereby obstructing the latter andcontaminating the vapors. By the introduction of the residue into theretort in a small continuous stream, its viscous nature is destroyedSerial Nb. 491,041.

shortly after it comes into contact with the hot surface of the retortand the swelling subsides quickly. Our experiments have shown thatbesides the advantages indicated, a much largerquantity of the residuecan be distilled by the continuous stream method than by placing a largequantity of the residue in the retort and distilling, assuming in thetwo cases, the same size retort and period of distillation.

The vapors resulting from the distillation, comprising a mixture ofgases and steam, are first passed through a cooling apparatus where theyare. cooled to approximately room temperature and then into a receivingvessel containing an acid in order to neutralize the amines and theammonia which are the chief constituents of the vapors. Eitherhydrochloric acid or sulfuric acid may be used for this purpose but acommercial B. sulfuric acid is preferred on account of its low cost. Thegas bubbles through the acid which absorbs the amines and the ammoniaand allows the noncondensable gases such as carbon monoxid and cyanogento pass into the atmosphere. It is preferred that the quantity of theacid used should be such as to leave the distillate slightly acid whenthe distillation is completed. The acidity of the distillate is testedduring the distillation from time to time, with litmus paper. As soon asit shows alkalinity, more acid is added. It is desired that thedistillate be kept slightly acid at the end of the distillation so thatthe amines will not be lost during the concentration of the distillate,the amines and ammonia being very volatile when not combined with theacid. The distillate is a mixture of two immiscible liquids, tar, and asolution comprising principally the amine sulfates and the sulfates ofammonia. The tar being lighter than the solution remains on top and maybe separated therefrom by drawing the solution from the bottom of thereceiving vessel.

The distillate obtained is concentrated in a vacuum evaporator at abouta 24-inch vacuum and at a temperature of 142 F., until most of theammonium sulphate crystallizes out. An analysis of the concentrateddistillate obtained in one of the operations showed the followingresult:

Most of the ammonium sulfate crystallizes out while the sulfates of theamines remain in a. liquid state. The ammonium sulfate is separated fromthe mother-liquor by ariy suitable method such as centrifuging. t

is not essential that the ammonium sulfate be separated from the motherliquor before the distillate is treated with a decomposing agent toliberate the amines, but it is desir- ,able if the ammonium sulfate isto be recovered as a by-product.

The concentrated mother-liquor preferably freed from most of theammonium sulfate is introduced into a steam-jacketed still, and adecomposing agent, for example, an alkaline earth or an alkali compoundadded, whereupon amine gases are liberated. Caustic soda orcausticpotash may be used for the liberation of the amines but as limeis just as eflicient and costs less it is preferred. It is quiteimportant that the lime be finel ground, so that approximately seventyveper cent thereof will pass through 80 mesh. It is further desirable thatthe lime contain at least 85% available calcium oxid. Lime of a poorquality and not of the proper fineness will cause a reduced yield, as itis not active enough to cause a complete liberation of the amines. Theamount of the lime added should be approximately 50% of the weight ofthe liquor treated. Very little heat is needed for the liberation of theamine gases, and the necessary amount is usually supplied by the actionof the lime on the amine sulfates and moisture contained in the liquor.Steam is used for heating the still only toward the end of thedistillation in order to complete the action of the lime on the aminesulfates. It is also quite important that the concentrated distillate beof the correct consistency. If it is thick, the lime will not thoroughlymix therewith and some of the amines will remain unacted upon. If it istoo thin, water vapor will pass along with the amine gases diluting theatter, which is undesirable. Experience has shown that a distillatehaving a gravity between 36 and 40 Be. is desirable.

The retort-tar .contains a considerable proportion of amines and thesemay be recovered by allowing the tar to stand for a period suflic-ientto enable it to separate from the associated water and thereafterdistilling with powdered lime, preferably in an amount equal to 40% ofthe weight of the tar.

The amine gases produced are conducted into carbon bisulfid undilutedwith any associating medium contained in a vessel provided with awater-cooled jacket whereupon amino ammonium salts of (1) monomethyldithiocarbamic acid, (2) dimethyl dithiocarbamic acid and (3) methylester of dimethyl dithiocarbamic acid are formed. The reaction may berepresented by the following equations:

' NHCHs 1. znmcnwcsi cs\sNHaCHa /N(CH3)Q SNH1(CHa)2 monoi scH,

Ex eriments have shown that it is decided y more advantageous to formthe amino-ammonium salts of dithiocarbamic acid by passing the aminegases into carbon bisulfid than into an alcoholic solution of carbonbisulfid. The disadvantages resulting from passing an alcoholic solutionof the amines into carbon bisulfid are practically the same as thoseresulting from passing a solution of the amines into an alcoholicsolution of carbon bisulfid. The advantages connected with the use ofstraight carbon bisulfid are as follows:

1. It is easier to separate the amino-ammonium salts of dithiocarbamicacid, as the latter are practically insoluble in straight carbonbisulfid, whereas in a mixture of carbon bisulfid and alcohol they aresoluble to a considerable extent.

2. The formation of ammonium sulphocyanate which forms by the action ofammonia on carbon bisulfid in the presence of alcohol is prevented to alarge extent. It is quite desirable to reduce the formation of ammoniumsulphocyanate to a minimum.

3. With the elimination of alcohol the production-cost is considerablyreduced.

It is necessary to provide a Water-cooled jacket for the carbon-bisulfidcontainer in order to efliciently effect the combination of the amineswith the carbon bisulfid. The reaction between an absorbing liquid suchas carbon-bisulfid. and the amines is an exothermic one and unless theexcess of heat is dissipated the absorbing liquid will vaporize causinga considerable loss of this agent. In addition, when the absorbingliquid is hot, the action of amines therewith is not complete, some ofthe latter escaping without combining with the absorbing medium.

The amino-salts are substantially insoluble in carbon bisulfid and maybe separated from the mixture by treating the same with a solvent of theformer immiscible with the latter. Alcohol will dissolve the aminosaltsbut as it mixes with carbon bisulfid and cannot be easily andeconomically separated therefrom it is not a suitable solvent. Ether andchloroform are subject to the same obections. Water is the most suitablesolvent. Vhen the mixture of the aminoammonium salts of dithiocarbamicacid and carbon bisulfid is treated with water the aqueous solution ofdithiocarbamic salts forms as a layer upon the heavier bisulfid whichmay be withdrawn leaving the substantially pure dithiocarbamic saltsolution, from which the salt may be recovered by suitable methods. Theamino-ammonium salts may also be recovered from the carbon bisulfid bycentrifuging.

We claim:

1. The process of producing dithiocar carbon bisulfid to formamino-ammonium salts of dithiocarbamic acid, addin 4 to the mixture ofthe amino-ammonium dithiocarbamic salts and carbon bisulfid a solvent ofthe former immiscible with the latter, and recovering the amino-ammoniumdithiocarbamic salts.

4. The process of producing dithiocarbamic compounds comprisingdistilling beet sugar residue, separating the amines from the ammoniumcompounds, passing the amines into carbon bisulfid to form aminoammoniumsalts of dithiocarbamic acid and recovering the latter.

5. The process of producing alkyl dithiocarbamic compounds comprisingdistilling beet sugar residue, collecting the distillation vapors in a.liquid menstruum, adding to the liquid menstruum containing the amines afinely-divided decomposing agent to liberate the amines, treating thelatter with carbon bisulfid, adding to the mixture of the amino ammoniumdithiocarbamic salts and carbon bisulfid a solvent of the formerimmiscible with the latter, and recovering the aminoammoniumdithiocarbamic salts.

6. The process of producing dithiocarbamic compounds comprisingdistilling beet sugar residue, collecting the distillation vapors in aliquid menstruum, adding a decomposing agent to the latter to liberatethe amines,

. adding to the liquid menstruum containing the amines a finely-divideddecomposing agent to liberate the amines, treating the latter withcarbon bisulfid, adding to the mixture of the amino-ammonium dithiobisulfid, adding water to the mixture of the amino-ammoniumdithiocarbamic salts and carbon bisulfid, and recovering theamino-ammonium dithiocarbamic salts.

10. The process of producing alkyl dithiocarbamic compounds comprisingintroducing beet sugar residue in continuous streams into a retort whileheating the latter to effect destructive distillation of the residue,collecting the distillation vapors in a liquid menstruum, adding to theliquid menstruum' containing the amines a finely-divided decomposingagent to liberate the amines, treating the latter with carbon bisulfid,adding to the mixture of the amino-ammonium dithiocarbamic salts andcarbon bisulfid a solvent of the former immiscible with the latter, andrecovering the aminoammonium dithiocarbamic salts.

11. The process of producing alkyl dithiocarbamic compounds comprisingdistilling beet sugar residue, collecting the distillation vapors in aliquid neutralizing menstruum, adding to the liquid menstruum containingthe amines finely-divided lime to liberate the amines, treating thelatter with carbon bisulfid, adding to the mixture of amino-ammoniumdithiocarbamic salts and carbon bisulfid a solvent of the formerimmiscible with the latter, and recovering the amino-ammoniumdithiocarbamic salts.

12. The process of producing alkyl dithiocarbamic compounds comprisingsubjecting beet sugar residue to destructive distillation, adding aneutralization agent to the vapors resulting therefrom in a quantitysufficient to keep the distillate slightly acid, concentrating theneutralization-product, adding a decomposing agent to the same,distilling the reaction-product to produce amine gases, treating thelatter with carbon bisulfid to form amino-ammonium salts ofdithiocarbamic acid, and recovering the latter.

13. The process of producing alkyl dithiocarbamic compounds comprisingdistilling beet sugar residue, collecting the distillation vapors inaliquid neutralizing menstruum, adding to the liquid menstruum containingthe amines finely-divided lime to liberate the amines, treating thelatter with carbon bisulfid, adding water to the mixture of theamino-ammonium dithiocarbamic salts and carbon bisulfid, and recoveringthe amino-ammonium dithiocarbamic salts.

14. The process of producing alkyl dithiocarbamic compounds comprisingintroducing beet sugar residue in continuous streams into a retort whileheating the latter to effect destructive distillation of the residue,adding a neutralizing agent to the vapors resulting therefrom in aquantity sufiicient to keep the distillate slightly acid, concentratingthe neutralization-product, adding a decomposing agentsto the same,distilling the reaction-product to produce amine gases,

treating the latter with carbon bisulfid tov bamic compounds comprisingintroducing beet sugar residue in continuous streams into a retort whileheating the latter to effect destructive distillation of the residue,passing the distillate into carbon bisulfid to form amino-ammonium saltsof dithiocarbamic acid, and recovering the latter.

16. The process of producing alkyl dithiocarbamic compounds comprisingintroducing beet sugar residue in continuous streams into a retort whileheating the latter to' effect destructive distillation of the residue,cooling the vapors resulting therefrom, adding a neutralizing agent tothe latter in a quantity sufficient to keep the distillate slightlyacid, concentrating the neutralization-product, adding adecomposing-agent to the same, distilling the reaction product toproduce amine gases, treating the latter with carbon bisulfid to formamino-ammonium salts of dithiocarbamic acid, and recovering the latter.

17. In the process of producing dithiocarbamic compounds by utilizingbeet sugar residues as one of the reacting materials, the step ofintroducing the residue in continuous streams into the retort whileheating the latter to effect destructive distillation of the residue.

In testimony whereof, I have hereunto subscribed my name this 27th dayof July,

STUART B. MOLONY. In testimony whereof, I have hereunto subscribed myname this 20th day of July, 1921.

YASUJURO NIKAIDO. v

